Shades used for covering window openings and the like are commonly raised and lowered, to change the extent of blockage of an opening, by winding and unwinding—or reeling and unreeling, the shade on a roller. In the past, a roller has been driven in various ways, including by having a manually driven shaft, called a wand here, which is connected to the roller by a universal joint, a flexible shaft, a gear box and so forth. A universal joint (also called a U-joint) is a familiar mechanical fitting which allows the axis of a rotatable driving member to be offset from the axis of the driven member. U.S. Pat. No. 1,744,686 of Pease shows a relatively crude universal joint comprising two interlaced loops, for driving a gear system of a roller. U.S. Pat. No. 7,204,292 of Nien shows a universal joint in combination with a worm gear which drives a roller.
Particularly when the fabric of a shade is heavy, the weight of the hanging-down portion of the shade can cause the roller to turn, thus allowing the shade to unwind from its desired set position. Such kind of motion is sometimes referred to here as counter-rotation. Counter rotation can be resisted when there is a universal joint connected to the roller. If a wand or other driver which is connected to the joint is put at a sharp offset angle to the axis of the roller then the weight of the wand or slight holding force applied to it will resist rotation at the joint.
Another option is to interpose a gear box, for instance a worm gear box, between the wand and roller, because such a system by its nature resists counter rotation. Another way is to lock a wand against counter-rotation when there is only a flexible shaft connecting the wand and the roller. For example, the wand can be fastened to a window frame. Still another way is to make the handle-end of the wand hinged, so it can form a crank end that extends at an angle to the length of the rest of the wand; and the crank end may contact a window frame or a fitting or the shade itself.
However, there are situations in which it may be undesirable to have an element on the window frame to which the handle of a wand attaches, or to have a wand which has a crank end. Gear boxes may be expensive or slow down the speed at which the roller may be driven. When a universal joint is not well-aligned, i.e., when the driver is at a substantial angle to the driven parts, it may require a lot of force to turn the roller, and the motion can be unsmooth and difficult to the user.
Improved ways are still being sought, to simplify and improve the operation of a window treatment which is raised and lowered.